28 SUMMARY OF CURRENT RESEARCHES RELATING TO 



arrangement for the nutrition and multiplication of the blastomeres, 

 which only after a long period become differentiated into the germinal 

 layers. 



Development of Heart in Ciona intestinalis.* — Marc de Selys 

 Longchainps finds that the pericardium has a paired symmetrical origin, 

 intimately united with the ventral encloderm of the pharynx. Thejoeri- 

 cardium is quite independent of the epicardium both in time and in mode 

 of origin. The two pericardial vesicles increase in size and embrace one 

 another, forming a vesicle divided into halves by a double septum. 

 Willey's account of the origin of the heart-cavity by a separation of the 

 components of the double septum is confirmed. 



INVERTEBRATA. 



Metazoa of Salt Lakes.f— Prof. P. Butschinsky previously gave an 

 account of the Protozoa of the Chadjibej-Liman and the Kujalintzky- 

 Liman at Odessa, and now gives lists of the higher forms found in the 

 lakes. The salinity in the former lake varies from 5-7° Beaume, and 

 in the latter from 9-9^° B. ; but while the water of the Chadjibej- 

 Liman differs from sea-water only in its concentration, that of the 

 Kujalintzky-Liman contains no sulphate save that of lime. As might 

 be expected, the Metazoa are few in number, not only absolutely but 

 also relatively to the Protozoa, and are fewer in the dense waters of the 

 Kujalintzky-Liman than in those of the Chadjibej-Liman. For the 

 same lake the number of Metazoa varies with varying salinity, Daphnia 

 brachiata appearing when this falls to 5° B., and Artemia salina dis- 

 appearing when it approaches saturation point. Generally, the fauna 

 may be said to consist of fresh-water, marine, and saline forms, and of 

 these the marine forms live chiefly on the banks. The greatest adapt- 

 ability to varying conditions among the representatives of the Metazoa 

 is displayed by the Crustacea, as is shown by their occurrence in water 

 of very varying salinity. 



Fauna of Salcombe Estuary4— Messrs. E. J. Allen and R. A. Todd, 

 with the assistance of W. Garstang, W. J. Beaumont, T. V. Hodgson, 

 and E. H. Worth, have given an account of the fauna of this estuary, 

 which was the hunting ground of Montagu. As the authors say, " It 

 is only by a large number of detailed records of this kind, where all 

 possible information is given as to the exact localities and conditions 

 in which each species is found, that we can hope to ascertain the general 

 principles which underlie the distribution of the animals which live in 

 the sea." 



Tentaculites and Nowakia. § — Herr G. Gtirich discusses these 

 Silurian fossils, and emphasises especially the importance of the em- 

 bryonic vesicle or nucleus in Noivakia, which points to the relationship 

 of this genus with Molluscs (Pteropods), while Tentaculites ornatus, 

 T. schlotheimi, T. sandbergeri, T. ienuicincius, &c. seem to be genuine 

 worm-tubes. 



* Bull. Sci. Acad. Belg., 1900, No. G, pp. 432-41 (6 figs.). 



t Zool. Anzeig., xxiii. (1900) pp. 495-7. Cf. this Journal, 1897, p. 300. 



t Journ. Mar. Biol. Ass., vi (1900) pp. 151-217 (1 chart). 



§ Jahresber. SSchles. Ges., lxxvii. (1900) pp. 32-5. 



